Automatic injection device with reset feature

ABSTRACT

The present invention relates to a dose setting and expelling device comprising a drive member and a dose setting mechanism which simultaneously sets a given dose and stores the energy necessary for a subsequently driving the drive member in order to expel a dose of medicine from an injection device. According to the invention the dose setting mechanism allows adjustment in both directions, such that a given set dose can be reduced or cancelled by reversing the input motion, typically by rotating a setting member backwardly, this in contrast to the known devices which either requires an additional release mechanism or which cannot be reversed at all.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/970,868, filed Oct. 22, 2004, which is a continuation of U.S.application Ser. No. 10/038,781, filed Jan. 2, 2002 (U.S. Pat. No.6,899,699), which claims the benefit under 35 U.S.C. 119 of Danishapplication PA 2001 00018, filed Jan. 5, 2001, and of U.S. provisionalapplication 60/260,602, filed Jan. 9, 2001, the contents of which arehereby incorporated by reference.

FIELD OF INVENTION

The present invention relates in general to a dose setting and expellingdevice for use in conjunction with an injection device comprising areservoir containing a fluid. In a more narrow aspect the presentinvention relates to a portable apparatus comprising such a dose settingand expelling device and adapted to accommodate a drug-containingampoule or cartridge. In an even more narrow aspect the presentinvention relates to a pocket-size injection device for repetitivesubcutaneous injection of individually set doses of a drug from areservoir placed in the device. The injection device may be in the formof a pen shaped syringe device, the cartridge being replaceable orintegrally formed with the device.

BACKGROUND OF THE INVENTION

Injection devices, typically in the form of pen shaped syringes, areespecially used by diabetics who have to inject themselves frequentlywith an insulin preparation to keep their blood glucose level withintolerable limits. However, recently different kinds of medicine, forexample growth hormone, have been administered in the same fashion.

The doses are mainly set by rotating, or dialing, part of the pensyringe relatively to the rest of the syringe and numbers forming ascale on the rotatable part of the syringe are moved in relation to anindicating mark on the rest of the syringe to indicate the set dose.When the user sets the dose, the syringe is actuated in order to expressthe dose of medicine. The actuation is normally provided by the userpressing some kind of button by a single movement up to a stop. Thismakes the injection stage independent of any need to assess what dose isbeing injected.

The injection device should be as simple as possible to use, i.e. thenormal use should only imply setting a dose and injecting the set dose,and both these steps should be simple to perform and this condition ismet by most prior-art pen devices.

However, for some users the actual step of expression the dose causesanxiety and a device which automatically expressed the dose on demandwould be desirable. Such a facility also could provide for a morerepeatable and smooth injection of the fluid. According to U.S. Pat. No.5,104,380 this has been achieved by a syringe device comprising a bodyand a rotatable dose setting device mounted on the body and capable ofbeing moved to a selected set position, a latch arranged to retain thesetting device in the set position, and means arranged to release thelatch to cause the set dose to be expelled. Movement of the dose settingdevice to the selected set position is accompanied by rotationalstraining of a spring, which, when the latch is released, provides theforce for expelling the set dose. When the latch is released, thesetting device is returned to an original position to drive a plungerthrough a one-way clutch to expel the set dose. The disclosed drivingmeans comprises a quick pitch screw thread arrangement for transformingrotation of the setting device into linear movement of the plunger. Thebody is adapted for receiving a cartridge containing a fluid to beinjected by having a cartridge container removable from the body forinsertion of a cartridge and then removal of the cartridge container isarranged to release the quick pitch screw thread device thus allowingthe plunger to be returned to an initial position.

However, not all pen syringes offer the opportunity to cancel a setdose, so if a dose once set is not wanted for injection the only way tobring the syringe back in its neutral position is to spill the dose.With syringes by which large doses may be set or in case the medicine isvery expensive, as is the case with growth hormone, this is notacceptable.

In order to solve this problem U.S. Pat. No. 5,626,566 discloses a penshaped syringe for repetitive injection of individually set doses of amedicine from a cylinder ampoule reservoir, comprising a dose settingmember which allow a dose set to be cancelled by incorporating meansprovided to release a unidirectional coupling between a piston drivemember and the dosing member. However, this design both requires arelease mechanism to be actuated when a dose is to be reset as well as amanual actuating mechanism when the medicine is to be expressed.

SUMMARY OF THE INVENTION

It is thus an object of the present invention to provide a dose settingmechanism which solves one or more of the above identified problems.

According to a first aspect of the invention, this is provided by a dosesetting device for an injection device (or apparatus), comprising adrive member and a dose setting mechanism which simultaneously sets agiven dose and stores the energy necessary for a subsequently drivingthe drive member in order to expel a dose of medicine from the injectiondevice, and where the dose setting mechanism allows adjustment in bothdirections, i.e. a given set dose can be reduced or cancelled byreversing the input motion, typically by rotating a setting memberbackwardly, this in contrast to the known devices which either requiresan additional release mechanism or which cannot be reversed at all.

In a preferred embodiment, the invention provides a device forrepetitive injection of individually set doses of a fluid or drug from areservoir, comprising: a housing, a reservoir containing a fluid to beexpelled, a drive member adapted to expel a dose of fluid from thereservoir, a spring means, a dose setting assembly mounted in thehousing and connected to the spring means, the dose setting assemblycomprising a member being moveable in a first direction to a selectedset Position against the spring means, wherein movement of the dosesetting member is accompanied by straining of the spring, and whereinthe dose setting device is moveable in a second direction to selectivelyadjust the set dose, a latch means associated with the housing to retainthe injection device in the set position against the bias of the springmeans, and the latch means being releasable to cause the drive member toexpel the set dose from the reservoir, the force for expelling the setdose being provided by the spring means. Preferably the injection deviceis adapted to receive a reservoir in the form of a replaceablecartridge.

In a preferred embodiment the housing comprises an internal thread, thedrive member being a longitudinal piston drive member (also termed drivemember or plunger) having an external thread corresponding to theinternal thread, the two threads having a pitch angle exceeding thefriction angle therebetween. Thereby the driving movement (i.e. theforward movement of the piston drive member) can be obtained by simplypressing the piston drive member axially forwardly a given distancedetermined by the set dose, this resulting in a rotative movement of thedrive member in the dosing direction. Such a thread is also known asnon-locking.

In a further preferred embodiment the dose setting device comprises acoupling member in displaceable engagement with the dose setting member,the spring means acting on the coupling member which in turn acts on thedose setting member. Preferably, the dose setting member has an internalthread, the dose setting member being rotationally mounted on the drivemember, and the coupling member arranged in sliding, non-rotationalengagement with the piston drive member, the spring means acting on thecoupling member in a direction corresponding to a longitudinal axis ofthe drive member; the dose setting member and the coupling membercomprise mutually cooperating surfaces such that rotation of the dosesetting member in order to set a dose results in straining of the springmeans as the coupling member is driven backwardly.

Preferably the thread between the dose setting member and the pistondrive member is of the non-locking type, however this necessitates acoupling or “brake” between the dose setting member and the couplingmember as otherwise the spring means would automatically be allowed toexpand thus driving the dose setting member backwardly to its initialposition. However, according to the stated object of the invention, thecoupling should allow the dose setting member to be rotated backwards inorder to selectively adjust the set dose.

In other words, the coupling between the dose setting member and thecoupling member should allow the dose setting member to be rotated ineither direction, yet preventing the spring means to counter rotate thedose setting member. This object can be achieved by providing a couplingbetween the above-described cooperating surfaces of the dose settingmember and the coupling member, the coupling providing a resistanceagainst rotation which is sufficiently to prevent the spring means tocounter rotate the dose setting member, the resistance being easilyovercome by a user rotating the dose setting member in either direction.In this way the user can “dial up” and “dial down”.

In preferred embodiments a bi-directional coupling between the dosesetting member and the coupling member is provided by coupling partshaving circular surfaces provided with sector shaped teeth having rampshaped edges, the surfaces being forced against each other with the rampshaped edges of the teeth on one surface abutting the ramp shaped edgesof the teeth on the other surface. When the dose setting member isrotated in either the dose setting or adjusting direction, the teeth onthe coupling parts will slide with their ramp shaped parts over eachother, whereby the dosing member is axially displaced against the forceof the spring and will jump back each time a top of the teeth isreached. Each jump back may be heard and/or sensed by the operator, andthe pitch of the too thing may be chosen so that a jump back takes placeeach time the dose setting is increased by say one unit.

In a further preferred embodiment the coupling is a frictional couplingprovided between cooperating surfaces, the necessary compression forcebetween the two surfaces being provided by the spring means acting onthe coupling member. The two coupling surfaces could be provided by anysuitable combination of materials and surface configurations providingthe necessary friction.

If a more simple construction is desirable, the above describedarrangement with a coupling member can be dispensed with. Therefore, ina further preferred embodiment the dose setting device comprises a dosesetting member having an internal thread, the dose setting member beingrotationally but frictionally mounted on the drive member, the frictionbetween the dose setting member and the drive providing a resistanceagainst rotation which is sufficiently to prevent the spring means tocounter rotate the dose setting member, however, the resistance beingeasily overcome by a user rotating the dose setting member in eitherdirection.

In order to provide an indication of the set dose, the dose settingmember may comprise a sleeve with numbers printed along a helical linewhich can be inspected through an opening, or window, in the housing ofthe device, the opening allowing only a portion, preferably on only one,of the numbers on the sleeve. When the sleeve is rotated andsimultaneously axially displaced along with the opening a numberindicating the actually set dose can be inspected through opening.

In a preferred embodiment the non-rotational engagement between thecoupling member and the drive member is established by a non-circularopening in the coupling member through which the correspondinglynon-circular drive member slides, for example provided by opposedflattened surfaces.

In a further preferred embodiment, a setting member is provided whichcan be rotated without any axial movement, the rotation beingtransferred to the dose setting member, this allowing a dose settingdevice of constant length. The setting member could be in the form of aknob, a ring or a skirt.

According to a second aspect of the invention, there is provided a dosesetting device for an injection device, comprising a drive member and adose setting mechanism which simultaneously sets a given dose and storesthe energy necessary for a subsequently driving the drive member inorder to expel a dose of medicine from the injection device, and wherethe dose setting mechanism can be released resulting in a re-setting ofthe dose, i.e. to the initial “0” position, after which the dose can beset again. Such a type of resetting arrangement could advantageously beused with a device of the type known from U.S. Pat. No. 5,104,380.

When used as part of an injection device, the injection device typicallycomprises a compartment into which a fluid containing reservoir can beinserted and locked in position, the reservoir comprising a relativelysmall opening at a foremost end (where typically an injection needle isarranged to provide communication with the interior of the reservoir,the reservoir being supplied in a sealed condition) and a rearmost endclosed by a piston in sliding engagement with an internal surface of thereservoir, a medicament being enclosed between the opening and thepiston, the dose setting and expelling device of the present inventionbeing arranged such that the piston drive member can be brought intocontact with the piston, this resulting in a dose of fluid or drug beingexpelled as the drive member is moved forwardly by the spring meansaction. Indeed, in order to properly set a desired dose, the dosesetting device and the cross-sectional area of the piston have to beadapted to each other.

In a further aspect of the present invention, a method for infusing aflowable drug into a living subject is provided, comprising the steps ofproviding an injection device for repetitive injection of individuallyset doses of a fluid (or drug) from a reservoir, the injection devicecomprising a housing, a reservoir containing a fluid to be injected andhaving an outlet means therefore, a drive member adapted to expel a doseof medicine from the reservoir, a spring means, a dose setting assemblymounted in the housing and connected to the spring means, the dosesetting assembly comprising a dose setting member being moveable in afirst direction to a selected set position against the bias of thespring means, wherein movement of the dose setting member is accompaniedby straining of the spring, and wherein the dose setting member ismoveable in a second direction to selectively adjust the set dose, alatch means associated with the housing to retain the device in the setposition against the bias of the spring means, and the latch means beingreleasable to cause the drive member to expel the set dose from thereservoir, the force for expelling the set dose being provided by thespring means, the method comprising the further steps of establishing aflow connection between the outlet means and the subject, selecting adose by operating the dose setting member, and releasing the latch meansto cause the drive member to expel the set dose from the reservoir. Inpreferred embodiments of the method, an infusion device as describedherein is used.

As used herein, the term “drug” is meant to encompass anydrug-containing flowable medicament capable of being passed through adelivery means such as a hollow needle in a controlled manner, such as aliquid, solution, gel or fine suspension. There is essentially nolimitation on the type of liquid drug which can be used with theinvention other than to exclude those liquid drugs which would beinappropriate to deliver to the subject in a fashion using the injectiondevice of the invention. Representative drugs include peptides,proteins, and hormones. In the description, the preferred embodimentswill be suitable for use with insulin. Correspondingly, the term“subcutaneous” infusion is meant to encompass any method of infusioninto a subject.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be further described with referencesto the drawings, wherein

FIG. 1 shows an external view of a pen-shaped syringe comprising adosing and expelling device according to a first embodiment of theinvention, and in a mode before dialling a dose,

FIG. 1A shows a cross section through the syringe in FIG. 1corresponding to the plane of the paper,

FIG. 1B shows a cross section through the syringe in FIG. 1 along theline B-B,

FIG. 2 shows an external view of the pen-shaped syringe of FIG. 1 in amode of dialling a dose (which is not apparent from the outside in thisrepresentation),

FIG. 2A shows a cross section through the syringe in FIG. 2corresponding to the plane of the paper,

FIG. 2B shows a cross section through the syringe in FIG. 2 along theline B-B,

FIG. 3 shows an external view of the pen-shaped syringe of FIG. 1 in amode after injecting a dose (which is not apparent from the outside inthis representation),

FIG. 3A shows a cross section through the syringe in FIG. 3corresponding to the plane of the paper,

FIG. 3B shows a cross section through the syringe in FIG. 3 along theline B-B,

FIG. 4 shows a housing member,

FIG. 5 shows a dose setting member,

FIG. 6 shows a piston drive member,

FIG. 7 shows a coupling member,

FIG. 8 shows a latch member,

FIG. 9 shows a locking member, and

FIG. 10 shows in partial a cross section through a pen-shaped syringecomprising a dosing and expelling device according to a secondembodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following the orientation of the different elements are describedwith help of the terms front and rear, respectively forwards andrearwards, denoting orientations toward left and right, respectively, inthe figures. The term longitudinal is used with reference to the generallongitudinal orientation of the shown syringe.

The syringe shown in FIG. 1 as seen from the outside comprises alongitudinal housing 10 with a first (rear) portion 11 and a second(front) portion 12, the first portion comprising a first compartmentwith the dose setting device of the present invention and the secondportion comprising a second compartment adapted to accommodate amedicine-containing ampoule or cartridge. In the shown embodiment thesecond portion is formed integrally with the first portion, however, thesecond portion is not part of the present invention and could,correspondingly, also be provided as a separate element which could beconnected to the first portion by, for example, a threaded or bayonetconnection. When removing the first portion, an empty cartridge (notshown) can be removed, the plunger (to be described below) can bereturned to its initial position, and a new cartridge can be insertedwhere after the portions again can be connected to each other. In casethe two portions are formed integrally, the foremost end of the firstportion should be closed by an additional element (not shown) in orderto provide a compartment for the ampoule.

The syringe further comprises a latch or trigger member 90 and a dosesetting knob 40 arranged at the rear end of the syringe.

As shown in FIG. 1A a partition member 20 is arranged between the firstand second portions, the partition member having an opening with aninternal thread 21, the partition thereby serving as a nut member,however; the term nut does not imply that the thread has to be definedby a bore but could also be defined between two opposed members. Alongitudinal plunger 30 serving as a piston drive member (i.e. when theplunger is positioned with its foremost end against a piston in theampoule) is arranged through the opening, the plunger having an externalthread 31 corresponding to the internal thread of the partition allowingthe plunger to be threaded through the opening. The thread of theplunger/nut connection has a pitch angle exceeding the friction angle ofthe nut and plunger. Thereby forward movement of the plunger can beobtained by simply pressing the plunger axially forwardly, thisresulting in a rotative movement of the drive member in the forwardsdirection. Such a thread is also known as non-locking. The plungerfurther comprises two opposed and parallelly arranged, planar sidesurfaces 32, 33 providing a “partial” external thread, however, this hasno functional influence on the thread connection as such. The purpose ofthe opposed surfaces will be apparent from the below.

The dose setting knob 40 comprises an outer cap portion 41 to be grippedby a user and an inner forwardly projecting cup-like skirt portion 42,the two portions being connected by a shaft 43 arranged through anopening 16 in the rear end wall 15 of the housing, whereby the knob isallowed to rotate but not to be axially displaced relative to thehousing.

The dose setting member 50 comprises a foremost end wall 51 and arearwardly arranged skirt portion 52. The end wall has an opening withan internal thread 53, the end wall thereby serving as a second nutmember through which the plunger 30 is arranged. The thread 53corresponds to the internal thread 21 thus allowing non-locking rotationof the plunger. The end wall further comprises a rearwardly facingcoupling surface 54 to be described below. The skirt portion 52 of thedose setting member comprises longitudinal grooves 55 on its innersurface engaging corresponding longitudinal tongue members 45 on theouter surface of the skirt portion 42 of the knob 40, whereby the twoskirt members are allowed to slide axially but not to rotate relative toeach other. Indeed, any suitable configuration could be used to providethis functional relation between the two skirt members. Numbers (notshown) are printed along a helical line on the external surface of theskirt 52 which can be inspected through a window 17 (see FIG. 4) in thehousing of the device, the window allowing only a portion, preferablyonly one, of the numbers on the sleeve to be inspected.

The tubular coupling member 60 comprises a foremost extension 61 with aforwardly facing coupling surface 62, as well as a rearwardly orientedtubular skirt portion 63. The skirt portion and the extension is formedwith two internal, opposed and parallelly arranged, planar surfaces 68,69 (see FIG. 7) corresponding to the opposed surfaces 32, 33 on theplunger, whereby the coupling member and the plunger are allowed toslide axially but not to rotate relative to each other. Indeed, anysuitable configuration could be used to provide this functionalrelationship between the plunger and coupling member.

A helical spring 70 is supported at its respective ends at an rearwardlyfacing surface 64 of the extension 61 and at an inner end surface 46 ofthe knob skirt, the spring thus providing a biasing force on thecoupling member. The shown spring may be replaced by any suitableelement which can store and release energy, for example a gas-filledmember or a foam body, such structures being examples of spring means.

The above-described coupling surfaces 54, 62 on the dose setting memberand the coupling member co-operate to provide a bi-directional couplingbetween the dose setting member and the coupling member. In the shownembodiment the coupling is provided by coupling parts having circularsurfaces provided with sector shaped teeth 57, 67 (see FIGS. 5 and 7respectively) having ramp shaped edges, the surfaces being forcedagainst each other by the spring 70 with the ramp shaped edges of theteeth on one surface abutting the ramp shaped edges of the teeth on theother surface. When the dose setting member is rotated in either a dosesetting or an adjusting direction, the teeth on the coupling parts willslide with their ramp shaped parts over each other, whereby the dosesetting member is axially displaced relative to the plunger (due to thethreaded connection) against the force of the spring and will jump backeach time a top of the teeth is reached. Each jump back may be heard andsensed by the operator, and the pitch of the too thing may be chosen sothat a jump back takes place each time the dose setting is increased bysay one unit.

A locking member 80 is provided on the plunger in order to prevent theplunger from rotating during the setting operation, i.e. during therotation of the dose setting member on the plunger. The locking memberis in the form of a wheel-like member comprising an opening 81 havingopposed and parallelly arranged, planar surfaces 83, 84 (see FIG. 9)corresponding to the opposed surfaces 32, 33 on the plunger, whereby thetubular portion and the plunger are allowed to slide axially but not torotate relative to each other. The locking member is arranged such thatit is allowed to rotate but not move axially with with respect to thehousing. The locking member further comprises a forwardly projecting,circumferential skirt with a plurality of axially aligned detents 82.

A latch member 90 comprising an inner latch arm 91 is arranged in thehousing wall, the latch member being moveable between a setting positionin which the latch arm engages between the detents on the locking memberthereby preventing the locking member and thus the plunger fromrotating, and a dosing position in which the latch arm disengages thedetents on the locking member thereby allowing the locking member andthus the plunger to rotate. Preferably the latch member is biasedtowards its setting position.

Next operation of the dose setting and expelling device of the presentinvention will be described with reference to the figures. When a freshmedicine-containing ampoule equipped with a fine needle (neither shown)is loaded into the syringe device, the piston in the ampoule is in itsrearmost position and the plunger is positioned with its foremost endagainst the piston. During use of the syringe the plunger moves thepiston forwards thereby expelling the medicine. FIGS. 1A and 1B show anintermediate position in which the plunger has been advancedapproximately half the full stroke length and with the dose settingmember in its “initial” position with a “0” showing in the window.

When setting a dose, the user preferably grips the housing with onehand, using the other hand to select (i.e. dial up) a desirable dose byrotating the dose setting knob 40. Due to the groove and tonguearrangement 45, 55 the dose setting member is rotated and threadedrearwardly relative to the plunger. During dose setting the user cancontrol the setting by inspecting the numbers printed on the dosesetting member as they pass the window, the numbers being indicative ofthe length the dose setting member has been rotated rearwards, and thusindicative of the subsequent stroke length for the plunger. If the doseis set too high, the user can simple adjust (i.e. dial down) the dose byturning the knob in the opposite direction until the numbercorresponding to the desired dose size shows up in the window.

As the dose setting member is rotated in either a dose setting or anadjusting direction, the teeth on the coupling parts will slide withtheir ramp shaped parts over each other, whereby the dose setting memberis axially displaced relative to the plunger (due to the threadedconnection) against the force of the spring and will jump back each timea top of the teeth is reached. As the coupling member is movedrearwardly the spring is compressed thus storing energy for thesubsequent dosing. This situation is illustrated in FIGS. 2A and 2B.

When the desired dose is set the user advances the needle through theskin and the syringe is ready to expel the set dose which is performedwhen the user depresses the latch member thus releasing the lockingmember 80 and thus the plunger which can now rotate freely.

The axial force exerted by the spring 70 is transmitted to the plungerthrough the coupling member 60 and the dose setting member 50(corresponding to the threaded connection) this resulting in arotational forward movement of the plunger due to the non-locking threadconnection between the plunger and the internal thread 21. As thecoupling member cannot rotate relative to the rotating plunger, the dosesetting member also rotates together with the plunger, this bringing thedose setting member back to its initial rotational position with a “0”showing in the window. This situation is illustrated in FIGS. 3A and 3B.

An “end of content” function (i.e. for the ampoule) is provided by thedose setting member simply abutting the rearmost portion 34 of theplunger as the threaded portion ends. The maximum possible dose is setwhen the rearmost end of the dose setting member abuts the rear end ofthe housing. The dose setting member is prevented from rotating past its“0” position as it abuts the partition wall.

The above-described device can either be provided for single use or forre-use in which case the dose setting mechanism will have to be reset,i.e. the plunger moved backwardly, in order to allow a new cartridge tobe inserted into the syringe. The plunger is moved backwardly simply byrotating the plunger, however, as the plunger is normally positionedinside a front portion 12 of the housing, the front portion shouldeither be removed in order to allow a user to properly grip the plunger,or the plunger should be rotated indirectly. The latter could beachieved by providing a housing having releasable front and rearportions 11, 12 (not shown) in order to allow the portions to be rotatedrelative to each other. As the front housing is rotated relative to therear housing and the dose setting member, the latched locking member 80,in sliding non-rotational engagement with the plunger, provides rotationof the plunger 30 which is then treaded rearwardly through the internalthreads 21, 53 of the partition member 20 respectively the dose settingmember. In order to prevent the dose setting member from rotating, theknob 40 should be gripped together with the rear housing in order toprevent relative rotation between these members. As the coupling member60 is in sliding non-rotational engagement with the plunger, it iscorrespondingly rotated resulting in a “clicking” relative rotationbetween the two mutually cooperating coupling surfaces 54, 62. When theplunger is brought to its rearmost position, the front and rear portionsare again locked to each other and the syringe is ready to be loadedwith a new cartridge.

The different members of the syringe and dose setting device shown inthe drawings of FIGS. 1-3 have been described in detail with referenceto these drawings, however, in order to provide an even betterunderstanding of the present invention, some of the members are shownindividually in FIGS. 4-9, FIG. 4 showing the housing, FIG. 5 the dosesetting member, FIG. 6 the piston drive member, FIG. 7 the couplingmember, FIG. 8 the latch member and FIG. 9 the locking member. In all ofFIGS. 4-9 the same reference numerals are used as in FIGS. 1-3 andbroken lines are used to indicate structures hidden behind surfaces.

Next an embodiment according to the second aspect of the invention willbe described with reference to FIG. 10 which in partial shows a pen-likesyringe with a dose setting device, comprising a drive member 102 and adose setting mechanism which simultaneously sets a given dose and storesthe energy necessary for a subsequently driving the drive member inorder to expel a dose of medicine from the syringe apparatus.

The syringe is generally pen-like, being of elongate cylindrical form,with a pen body 108 closed at its left-hand end in FIG. 10 by a plungerguide 111 screwed into the pen body and having a cylindrical bossextending to the left and being externally threaded to accommodate acartridge carrier 113 (shown in partial only). A cartridge of insulin(not shown) can be fitted into the cartridge carrier 113 before thecartridge carrier is screwed onto the boss on the plunger guide 111.

The guide 111 guides longitudinal movement of a drive plunger 102progressively into the open end of the cartridge as insulin is injectedthrough a needle (not shown) at the end of the carrier. The bore in theplunger guide has opposed flats for preventing rotation of the driveplunger 102 as it moves into the cartridge, the drive plunger havingcorresponding opposed flats.

Movement of the plunger 102 is achieved by energy stored in a helicalspring 106, which is twisted as a pre-set dose of insulin to be injectedis set by rotation of a cap 107 which can turn about a graduated sleeve112 at the right-hand end of the pen body 108. The cap 107 has a window(not shown) through which graduations can be read to show the anglethrough which the cap has been turned.

The cap is integral with a drive sleeve 101 which can turn in a plainbearing defined by the sleeve 112 and has an annular ring 125 projectingat its left-hand end and formed with a ring of ratchet teeth. The spring106 is secured, respectively, at its ends to a flange (not shown) at theleft-hand end of the drive sleeve 101 and a flange (not shown) on thesleeve 112 so that, as the cap is turned, the spring is strained bybeing partially wound up.

The spring is a compression spring and both when strained torsionallyand unstrained urges the teeth on the annular ring 125 of the drivesleeve into engagement with cooperating ratchet teeth 126 formed on agear member 103. The arrangement of the ratchet teeth is such that thecap and drive sleeve can be turned in relation to the ratchet gear inone direction only with turning being accompanied by a series of clicks,as each successive ratchet tooth is engaged, i.e. an one-way ratchetmechanism. The ratchet gear member 103 is normally held against rotationby engagement of external teeth on the gear member 103 with internalteeth on a latch member 109. The latch member 109 has a leg which extendthrough slots in the housing to prevent rotation of the gear member inrelation to the pen body, although the latch member can slide axially,as will be described later.

When the pre-set or “dialled up” dose of insulin is to be injected, thelatch member 109 is slid axially to the left out of engagement with theratchet gear member 103 so that the gear can rotate driven by the torqueof the spring 106 through the drive sleeve and the ratchet teeth.Rotation continues until the cap has returned to its initial positiondefined by a positive stop between the cap and the pen body. The latchmember is preferably biased towards its locked position by spring means(not shown).

The ratchet gear member 3 is internally threaded with a quick pitchthread to cooperate with a corresponding external thread on the stern ofthe drive plunger 102. Rotation of the ratchet gear and drive tapers isaccompanied by axial movement of the plunger along the quick pitchthread since the plunger stern cannot turn in the plunger guide 111.Thus, the plunger is driven into the cartridge, expelling the pre-setdose of insulin. When the cap stops turning on the pen body, the plungerremains part-way along the inside of the cartridge.

According to the invention, a second latch or locking member 119 isprovided which in its normal locked position slides on a rear surface ofthe annular ring 125 and thereby prevents the drive sleeve from movingrearwardly and thus to disengage from the gear member. However, if adose is set too high a user may move the locking member to the rightallowing the drive sleeve to be pulled backwards to thereby disengagethe ratchet teeth from the gear member in which position it can berotated backwardly to selectively adjust the set dose. As the drivesleeve is forced forwardly by the spring 106, it can only rotate whengripped and pulled backwardly by the user. When the dose has beenadjusted the locking member is moved to its locked position (properlysecured by any convenient means, either mechanically or by a springmeans) and the syringe is ready to be released for expelling a set dose.

In an alternative embodiment no second latch member is provided, theratchet gear members being held in engagement merely by spring meansallowing the drive sleeve to be pulled backwardly and out of engagementby a user. Proper engagement between the ratchet members when not pulledapart to re-adjust the device is provided by spring means, either by thespring 106 alone or by an additional spring means. In order to protectagainst unintended disengagement the teeth of the ratchet members couldbe “under-cut” such that the drive member has to be rotated slightlyforwardly as it is pulled rearwardly in order to disengage.

The procedure can be repeated until the cartridge is exhausted, afterwhich the cartridge can be replaced by unscrewing the cartridge carrier113 from the plunger guide 111.

While the present invention has been described in connection with thepreferred embodiment shown in the various figures, it is to beunderstood that other similar embodiments may be used or modificationsand additions may be made to the described embodiment for performing thesame function of the present invention without deviating there from. Forexample, although the above disclosed coupling provides a preferredsolution to desired dial up/dial down function, any coupling between thedose setting member and the coupling member allowing the dose settingmember to be rotated in either direction, yet preventing the springmeans to counter rotate the dose setting member could be used, thisincluding a manually actuatable coupling such as described above withrespect to FIG. 10. Further, in the shown embodiment most elements arearranged coaxially, however, this can be changed wherever specific needsmake this convenient for the skilled person. When it is described thattwo elements are acting together, this may imply that they are directlyor indirectly connected as long as the desired action is achieved.

Therefore, the present invention should not be limited to any singleembodiment, but rather construed in accordance with the appended claims.

1. An injection device for injecting medication from a cartridge, thedevice comprising: a drive member adapted to expel a dose of fluid fromthe reservoir, an elastic element for storing energy, wherein theelastic element comprises a torsion spring, a dose setting mechanismthat cooperates with the elastic element, the dose setting mechanismbeing rotatable in a dose setting manner consisting of rotating the dosesetting mechanism in a first direction to a selected set position,against a bias of the elastic element, wherein rotation of the dosesetting member stores energy in the elastic element for later use inexpelling a drug from the reservoir, and in a second manner to reducethe size of the set dose, when necessary, the second manner consistingsolely of rotating the dose setting member in a second directionopposite the first direction to selectively adjust the set position toreduce the size of the set dose without expelling medication from thedevice, a releaseable latch adapted to retain the dose setting member inthe set position against the bias of the elastic element, whereinrelease of the latch causes the dose setting assembly to drive the drivemember to thereby expel a set dose from a fluid-filled reservoir whenthe dose-setting device is used in combination therewith, the force forexpelling the set dose being provided by the elastic element, whereinnumbers are printed on an external surface disposed on the dose settingmember so that only a portion of the numbers pass through a window (17)during the setting of a dose, reduction of the size of a set dose, andexpulsion of a dose from the fluid-filled reservoir.
 2. An injectionsyringe for apportioning and injecting multiple doses of medication froma drug containing reservoir the injection syringe, the injection syringecomprising: a dose setting knob that is rotatable in two directions, adose indicator having a helically arranged scale of numbers, a windowfor displaying one of the helically arranged numbers, a latch, anelastic energy storing member for storing a sufficient amount of energyto expel a set dose of medication, the elastic energy storing memberstoring a force that induce a rotational motion between two threadedcomponents to create an axial movement of a member that transfers forceto the drug containing reservoir, wherein the dose setting knob ismanipulatable in a manner to set and selectively reduce the size of aset dose, when necessary, the manner consisting of rotating the dosesetting knob in a first direction to set a dose, wherein rotation of thedose setting knob in the first direction stores energy in the elasticmember, wherein the dose setting knob is freely rotatable in an oppositedirection without the need for additional operations by a user, whereinrotation of the dose setting member in the opposite direction acts toreduce the size of the set dose without expelling medication, therebyallowing the user to selectively adjust the set dose downward withoutexpelling medication, wherein when the latch is actuated it causesrelease of energy from the elastic member and wherein the releasedenergy from the elastic member is transferred to a reservoir containingmedication thereby expelling medication from the reservoir, whereinduring the expelling of medication as the dose indicator rotates towarda zero position, which is the position that the scale was in prior tosetting a dose, and wherein the rotation of the scale of numbersrelative to the window is visible in the window during setting, reducingand the expelling of a dose of medication and wherein only a portion ofthe numbers is visible in the window at any one time.
 3. The syringe ofclaim 2, wherein the elastic energy storing member is a torsion spring.4. A dose setting and ejecting mechanism for use in combination with aninjection device comprising a fluid-filled reservoir and a drive memberhaving an external thread that engages an axially fixed component withinthe device having an internal thread, wherein the drive member isadapted to expel a dose of fluid from the reservoir, the dose settingand ejecting mechanism being adapted for repetitive injection ofindividually set doses of fluid from the reservoir, the dose setting andinjecting mechanism comprising: a housing a spring mounted in thehousing, wherein the spring acts to store a torsional force for use increating relative rotational motion between the drive member and theaxially fixed component a dose setting assembly mounted in the housingand connected to the spring, the dose setting assembly comprising a dosesetting member being rotatable in a manner to set and adjust the size ofa dose, the manner consisting of rotating the dose setting member in afirst rotational direction to set the size of the dose and merelyrotating the member in a second and opposite direction to reduce thesize of the dose, when dose size reduction is necessary, wherein whenthe dose setting member is rotated in the second direction to reduce thesize of a set dose, no drug is expelled from the device, whereinselectively reducing the size of the set dose consists solely ofrotating the dose setting member in a second direction opposite that ofthe first direction a first direction and wherein rotating in the firstdirection is against the bias of the spring and results in the storageof energy in the spring for later use in expelling a drug from thereservoir, a releaseable latch adapted to retain the dose setting memberin the set position against the bias of the spring, wherein release ofthe latch causes the spring in the dose setting assembly to drive thedrive member to thereby expel a set dose from a fluid-filled reservoirin the injection device when the dose-setting device is used incombination therewith, the force for expelling the set dose beingprovided by the spring, wherein release of the latch causes the springto induce a relative rotational motion between the drive member and theaxially fixed component having the internal thread thereby driving thedrive member in a distal direction, and wherein numbers are printedalong a helical line to form a scale on an external surface of arotatable skirt so that only a portion of the numbers pass through awindow in the housing during the setting of a dose, during dose sizereduction without expulsion and during expulsion of a dose duringinjection from the fluid-filled reservoir, when the skirt rotates. 5.The dose setting and ejecting mechanism of claim 4, wherein the dosesetting and ejecting mechanism is integral to a medication deliverydevice comprising a cartridge of medication used to treat diabetes. 6.The dose setting and ejecting mechanism of claim 4, wherein the dosesetting and ejecting mechanism is integral to a medication deliverydevice comprising a cartridge of medication used to treat a conditionthat requires self injections.